Abstract:

Chromosomal abnormalities are a major cause of the structural anomalies detected during early fetal ultrasound screening. We report two cases of early fetal nuchal translucency (NT) abnormalities linked to chromosomal copy number variations (CNVs) and their origins. G-banding karyotype analysis was conducted on amniotic fluid cells of the fetuses and the peripheral blood of their parents, supplemented by single nucleotide polymorphism array (SNP-array) analysis of fetal amniotic fluid cells. For case 1, karyotype analysis revealed 46,Xn,der(4)del(4)(q35.2)dup(4)(q35.2q26), and the SNP-array results identified terminal deletion with partial inversion duplication on chromosome 4q, confirming 4q inversion duplication with terminal deletion syndrome. For case 2, the karyotype was 46,Xn,der(X)del(X)(p22.23)dup(X)(p22.31p11.1), and SNP-array analysis detected a 49.414 Mb duplication in the Xp22.31p11.1 region, consistent with Xp inversion duplication with terminal deletion syndrome. Both cases were de novo mutations. The integration of karyotype and SNP-array analyses successfully determined the genetic causes of NT abnormalities in these cases, providing a solid foundation for subsequent reproductive guidance.

Key words: Prenatal diagnosis, Inversion duplication syndrome, Single nucleotide polymorphism microarray, Chromosomes, Karyotyping